Operating machinery (working machines) such as excavators and dump trucks employed in mines is required to be operating 24 hours a day. If the machines are stopped due to failures, their shutdown could significantly impact on ongoing operations. In order to keep up the sound operation status, maintenance should be performed frequently. This maintenance generally involves scheduled one mainly in reference to the operation hours of machinery. The machine parts specified by design criteria are inspected, repaired, or replaced with new parts in accordance with the operation hours of the machines involved.
In recent years, the above-mentioned scheduled maintenance has been supplemented with condition-based maintenance (CBM; e.g., see Patent literature 1). In it, the data collected from diverse sensors mounted on the operating machine are subjected to diagnosis so that an abnormality of the machine will be detected earlier and the machine will be properly maintained before it breaks down. This practice is intended to prevent an unexpected outage of the machine between instances of scheduled maintenance so that the impact of the outage, should it occur, is minimized.